1. Field of the Invention
The present invention relates to a molded gear formed by cooling and solidifying a molten material such as a plastic, a metal and the like in a mold, and particularly, to a molded gear having a function as a cooling fan.
2. Description of the Related Art
In recent years, many injection-molded plastic gears as molded gears are used in an Office Automation (OA) system, an Audio Visual (AV) system, an electric/electronic system, and an automobile part or the like. Such injection-molded plastic gear has a light weight and a self-lubricating property; generates a noise lower than that in a metal gear, and can be produced in bulk, leading to an economic advantage. Therefore, the injection-molded plastic gear has been utilized in a further widened range of application.
However, such injection-molded plastic gear has a relatively poor thermal conductivity and for this reason, heat is liable to be accumulated in the tooth faces and hence, the plastic gear has a characteristic that its mechanical nature is dependent on the heat.
In recent years, the OA system, the AV system or the like is designed at a reduced size, so that the space for accommodation of the gear is smaller, but also an unoccupied space is as small as possible. Therefore, even when the cooling of the part is required in the OA system, the AV system or the like, a cooling fan cannot be disposed freely in some cases.
Accordingly, it is an object of the present invention to provide a molded gear having a function as a cooling fan, so that a forcible convection (flow of air) can be produced within a space having the molded gear accommodated therein.
To achieve the above object, according to a first aspect and feature of the present invention, there is provided a molded gear made with a plurality of teeth formed around an outer periphery thereof by cooling and solidifying a molten material in a mold, comprising a plurality of holes defined circumferentially in a portion radially inner than the teeth to extend through such radially inner portion from a surface to a back, and blades formed at side edges of the holes.
With such configuration, when the molded gear is rotated, a flow of air passed through the holes from the surface side to the back side of the molded gear can be generated by the blades and blown to a part such as an integrated circuit (IC), a motor and the like disposed adjacent the molded gear to cool it, and heat-accumulated air around the IC, the motor or the like can be forcibly discharged to inhibit the rise in ambient temperature. Particularly, the molded gear according to the present invention has the fan function and hence, it is possible to supply air to an area whore a fan cannot be specifically placed, thereby cooling such area. In the molded gear according to the present invention, the holes are defined adjacent the teeth and the blades are formed at side edges of the holes. In this case, the flow of air is produced by the blades to flow in the vicinity of the teeth, whereby the heat in the teeth and in the vicinity of the teeth can be taken away by the heat transfer and hence, the cooling of the teeth and an area in the vicinity of the teeth cab be achieved effectively.
According to a second aspect and feature of the present invention, there is provided a molded gear made with a plurality of teeth formed around an outer periphery of a rim by cooling and solidifying a molten material in a mold, comprising a plurality of blades formed at distances circumferentially on an inner peripheral surface of the rim, and a radially inner portion formed on the side of inner peripheries of the blades to support the rim through the blades.
With such configuration, when the molded gear is rotated, the blades generate a flow if air directed from a surface to a back of the molded gear. As a result, a flow of air is along the inner peripheral surface of the rim is produced, and the heat of the teeth and the rim is taken away by such flow of air, whereby the teeth and the rim are cooled. Thus, a reduction in mechanical strength of the molded gear due to a rise in temperatures of the teeth and the rim is inhibited. In addition, according to the present invention, the axial flow of air produced by the blades is blown to another part disposed adjacent the molded gear and hence, the part disposed adjacent the molded gear can be cooled.
The above and other objects, features and advantages of the invention will become apparent from the following description of the preferred embodiments taken in conjunction with the accompanying drawings.